This application is based on Application Ser. Nos. H10-180130, H10-198485 and H10-198486 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a projector that automatically adjusts projection parameters such as zoom ratio, focus, and convergence.
2. Description of Related Art
In the field of projectors, one example of a technology that automatically adjusts projection parameters such as convergence and focus is disclosed in U.S. Pat. No. 5,231,481. In this technology, a photographic device, such as a video camera, photographs an image that a projector projects onto a screen to obtain image data. An information processing apparatus such as a microcomputer then analyzes this image data to detect adjustment errors in the projection parameters and performs suitable corrections to the settings of the projector. The following describes the operation of this technology when automatically adjusting the focus of the projection lens.
FIG. 1 is a block diagram showing the construction of the projector 900 in this related art. As shown in FIG. 1, the projector 900 includes a projection lens 901, dichroic mirrors 902, 903, 906, and 907, mirrors 904 and 905, light valves 908, 909, and 910, a light source 911, an A/D convertor 915, a microcomputer 916, a test pattern generating circuit 929, and a projection lens focus adjusting mechanism 933. The image that this projector 900 projects onto the screen 980 is photographed by the video camera 990. The image photographed by the video camera 990 is subjected to A/D (analog to digital) conversion by the A/D convertor 915 and is then inputted into the microcomputer 916 as image data.
The microcomputer 916 analyzes the inputted image data and, based on the results of this analysis, controls the projection lens focus adjusting mechanism 933 to have the focus of the projection lens 901 adjusted. Note that while the optical paths from each of the light valves 908, 909, and 910 to the projection lens 901 appear to have different lengths in the example illustrated in FIG. 1, such paths can be easily adjusted using conventional technologies, such as through the use of additional lenses (not illustrated). As described in the embodiments of the invention, this problem can also be addressed by changing the positioning of the dichroic mirrors or other components.
As described above, the projector 900 of the above technology requires the further use of a video camera 990 to photograph the image projected onto the screen 980. This leads to the problems of a rise in the cost of the technology and of the user having to perform the difficult task of correctly orienting the video camera 990 toward the screen 980.
It is a primary object of the present invention to provide a projector that can automatically adjust the projection parameters with a simple operation while suppressing the cost of the overall equipment.
This primary object can be realized by a projector that projects images onto a screen by passing light from a light source through a light valve and a projection lens, the projector comprising: reflected light detecting means for detecting light that has been reflected off the screen and back through the light valve; and projection parameter adjusting means for adjusting a projection parameter based on a detection result of the reflected light detecting means.
With the stated construction, light reflected back off a screen is detected and used to adjust the projection parameters, so that there is no need to use expensive equipment, such as a video camera, for photographing an image projected onto the screen. Adjustments to the positioning of the video camera or other such additional equipment are also unnecessary, thereby making automatic adjustment possible with a simple operation.